Product counterfeiting is a major worldwide problem experienced in connection with many different products. It is estimated that 5% of all world trade in branded goods is counterfeit (ten Ham, Drug Saf., 2003, 26: 991-7). A counterfeit product often appears confusingly similar to that of a genuine product. The material of a counterfeit product may be the same as, or different from the material of a genuine product. Often the counterfeiting product has inferior quality as compared to that of a genuine product.
Drug counterfeiting has become a significant issue in the healthcare community and the pharmaceutical industry worldwide. A report published in the open-access health journal PloS Medicine suggests that up to 15 percent of all drugs sold worldwide—worth of $35 billion (25 bn)—are counterfeit. Drug counterfeiting threatens to impose great health risks to customers who buy the counterfeit drug in the expectation that they are buying a genuine drug. Because of the absence of safety regulations compared to authentic equivalents, counterfeit drugs often have substandard drug quality, quantity, or harmful ingredients. In addition, as a result of counterfeiting, legitimate pharmaceutical companies can lose significant revenues. It can be difficult to distinguish a counterfeit drug having a chemical formulation similar to that of a genuine drug, but made by substandard manufacturing procedures. Likewise, it can also be difficult to distinguish a counterfeit product produced by diluting the genuine product. A report released by the Center for Medicines in the Public Interest, in the United States, projects counterfeit drug sales to reach US$ 75 billion in 2010, a 92% increase from 2005.
Methods have been developed to identify genuine products and distinguish them from counterfeit products. For example, various analytical methods have been used to detect components in pharmaceutical products, with emphasis on the identification of differences among manufacturers that can be used for source verification in suspect/counterfeit cases. Such methods include, but are not limited to, capillary electrophoresis (Flurer et al, Journal of Chromatography, A, 1994, 674: 153-63), thin-layer chromatography (Pachaly et al., Pharmazeutische Industrie, 1993, 55: 259-67), near-infrared spectroscopy (Scafi et al, Analyst. 2001, 126: 2218-24; and Olsen et al., Pharmaceutical Technology North America, 2002, 26: 62-71), and calorimetric assay (Green et al, Tropical Medicine & International Health, 2001, 6: 980-982).
Other methods have been developed to establish identity and source of the product, sometimes including a pharmaceutical product, by marking the product. For example, bar code symbols placed on the outside of the medication may be used for prescription medication identification (U.S. Pat. No. 5,845,264); a mixture of at least two photochromic compounds that have different absorption maxima in the activated state may be incorporated into a carrier composition, e.g., ink, paint, fiber or polymer to form the authenticating display data on the article (U.S. Pat. No. 5,289,547); a solution of a target nucleic acid may be incorporated in an object for security crypto-marking of the object (U.S. Pat. No. 5,139,812); a hapten may be associated with the product as a marker (U.S. Pat. No. 5,429,952); compositions that are uniquely luminescent may be incorporated or applied to materials for verifying products or documents (U.S. Pat. No. 6,402,986); and constituents intrinsically located or extrinsically placed in an object (such as a pharmaceutical) may be detected by x-ray fluorescence analysis to identify or verify the object or its point of manufacture (US 20040022355). In addition, U.S. Pat. No. 5,599,578 describes a method for labeling an object for its verification by applying a mark to said object with a visible ink that contains a component that is invisible to the naked eye, such as a dye that is visible only in the presence of selected radiation, or an ink that displays a selected measurable electrical resistivity, or an ink containing a biologic marker. WO 2004041328 describes methods for marking a pharmaceutical product, container or pharmaceutical packaging system with a scent to establish the identity and/or source of the pharmaceutical.
The substance(s) used to mark a product can be visible, such as a dye or colored molecule. They can also be invisible to the unaided eyes, thus are a “covert” marker of a substance. Covert markers are typically more difficult to replicate, simulate, alter, transpose, and are less subject to tampering. WO 2005111127 describes a method for incorporating covert markers into an article in the form of metals and their salts and oxides into plastics, then detecting net changes in magnetic field around said article.
Microparticles have been used to mark a product for authentication. In some embodiments, microparticles have been used as the “cargo” to host the coding elements like molecules or nanoparticles with identifiable features (Finkel et al., Oct. 1, 2004, Analytical Chemistry, 352A-359A, and references therein). U.S. Pat. No. 4,053,433 describes a method of marking a substance with microparticles that are encoded with an orderly sequence of visually distinguishable colored segments that can be decoded with a microscope or other magnifying device. Additionally, microparticles have been used as part of the coding element, where the physical properties of the microparticles are used as the coding elements, and most code deciphering is accomplished by recognizing a physical pattern formed by the compilation of various microparticles (Finkel et al., 2004 supra and references therein). U.S. Pat. No. 4,767,205 discloses an identification method involving an identification code that is based upon a selected number of groups of microparticles, wherein each group is made of highly uniform microparticles of substantially the same uniform size, shape and color with the specific combination of size, shape and color in one group not being repeated in any other group. U.S. Pat. No. 6,647,649 discloses a process for marking an article by applying thereto a tag, which comprises a plurality of microparticles having two or more distinguishable marker layers corresponding to a predetermined numeric code.
Despite these efforts, drug counterfeiting remains a worldwide problem. There is a continuing need to develop novel methods to combat counterfeit drugs at the manufacturing stage and for detection in the distribution chain. One effective way to fight counterfeiting is to mark a product with a product authentication code that is not easily imitated or counterfeited.